pekkaa

I'm building my first standalone arduino project (atmega328 on stripboard). I power it through a 7805 regulator which has 10uF caps on input and output. The 7805 is on a separate circuit board. The wire from the 7805 to atmega328's VCC is about 20 cm (ten inches) long, quite thick (0.75mm2) wire, plus about ten cm on the stripboard.

Should I place an additional cap between atmega328's VCC and GND (and AVCC and GND) close to the pins? And what would be a proper size for the cap?

It wouldn't matter where the regulator and its electrolytics were, that 0.1uF cap is required always, right next to the chip. Decoupling capacitors should have low ESR and ESL, which in practice means ceramic, right next to the relevant pins. The exact value isn't too important,BTW, so anything from 0.1uF to 1uF will work fine.

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